The disclosure relates to a mining roof support frame, in particular a shield roof support frame, comprising a main frame, two base skids, and a base skids lifting device including at least one hydraulic lifting ram. The lifting ram can be mounted on a bridging member connecting the two base skids of the main frame. A pressure-generated force can be extended downward against a walking bar of a walking unit of the mining roof support frame located between the base skids. The disclosure concerns also the base skids lifting device for mining support assemblies itself.
Shield support assemblies with base skids lifting devices are of known art in various embodiments (DE 40 35 252 A1, DE 42 05 940 A1). The use of a base skids lifting device is particularly recommended in circumstances where the roof support frame with its base skids presses into the soft floor so deeply when in use as a result of the suspended load, that the walking process is impeded. The floor conditions can vary from site to site, and also can be subject to variations within the same site. If the hydraulic lifting ram is connected to the bridging member that connects the two base skids of the roof support frame and bridges across the walking unit channel between the two base skids, and the lifting ram is located such that in the retracted state it lies with its lower support foot below the lower edge of the bridging member, then it can occur, particularly in the case of uneven and very soft floors, that the base skids dig so deeply into the floor as a result of the suspended load that the retracted lifting ram makes contact with the walking bar and is subject to high loadings. This results inevitably in the destruction of the lifting ram, or to a shearing off of the lifting ram from the bridging member.
The known state of the art technology furthermore attracts the disadvantage that during servicing or repair tasks on the walking bar or walking ram, time-intensive bolting tasks are required for the disassembly and assembly of the connecting parts receiving the lifting ram from the bridging member that rigidly connects the base skids. In addition, the bolted joints that are used are subject to shearing forces. Moreover, the lifting ram with the connecting parts must be removed from its position or fixed in position manually by a miner working underground under difficult conditions.